Increased efficacy of early spinal cord stimulation in an animal model of neuropathic pain.

Although spinal cord stimulation (SCS) is an established treatment for chronic neuropathic pain, pain relief is still not successful in a large group of patients. We suggest that the success of SCS may be related to the timing of SCS during the development of chronic neuropathic pain. We therefore compared the effect of SCS applied after 24h of neuropathic pain (early SCS) and after 16days of neuropathic pain (late SCS). For early SCS, male Sprague-Dawley rats (n=13) were implanted with an SCS device, followed by a partial ligation of the sciatic nerve. Using von Frey monofilaments, tactile allodynia was assessed 24h after ligation. Animals with tactile allodynia received 30min of SCS. Withdrawal thresholds were assessed just before SCS, during SCS and until the return to pre-stimulation withdrawal threshold. Results were compared with the data from late SCS (n=29). Out of the 13 allodynic animals that received early SCS, 10 (77%) responded to SCS with significantly increased withdrawal thresholds, compared to 38% in the late SCS group. The increase of the withdrawal threshold in the early SCS group could still be noticed 90min after termination of SCS. In more than half of these animals, pre-stimulation withdrawal thresholds were reached only the next day. Early SCS resulted in an increased number of responders to SCS and furthermore an increased duration of the effect of SCS as compared to late SCS. Early SCS treatment of neuropathic rats is more effective as compared to the late SCS treatment.